1 (edited by orieblax 2015-11-03 23:14:52)

Topic: Problem with AES-CMAC when IV is different to 00...00

Im Using Fully Enciphered communication for Standard AES, got Authentication Session Ok (Session Key), then send a command to read a file with Fully Enciphered communication settings: bd02000000100000, and decrypt the answer with the IV updated using CMAC (with IV=00...00), read Ok, then i try with an IV updated (not zero's ) to calculate the CMAC again, but get a wrong CMAC value, and im getting errors when decrypt the response from the card because the final IV is wrong.

Resume: CMAC calculation works perfect only just after authentication when IV is reset to 00...00, but next CMAC calculation fails due to IV to calculate it has changed (not zero's ).

How can i implement AES-CMAC with IV different from 00...00 ?

I been trying with a example of the book "DESFire EV1 - Features and Hints"